1. Field of the Invention
The present invention relates to the field of magnetic random access memory (MRAM) and methods of writing and reading data using the MRAM. More particularly, the present invention relates to an MRAM using a thermo-magnetic spontaneous Hall effect and a method of writing and reading data using the MRAM.
2. Description of the Related Art
Giant MagnetoResistance (GMR) is derived by a variation in the resistance of a thin film depending on whether two adjacent magnetic layers are magnetized in parallel or counter-parallel directions when electrons pass through the two magnetic layers. GMR may be described with reference to spin-dependent scattering. Even when an insulating film, such as an aluminum oxide film (Al2O3), as opposed to a metallic film, is interposed between the two magnetic layers, spin-dependent scattering occurs. Spin-dependent scattering is referred to as Tunneling MagnetoResistance (TMR).
Conventional MRAMs are non-volatile memory devices using GMR or TMR. Accordingly, information recorded in these MRAMs is not lost even when power is off, which is in contrast with dynamic random access memory (DRAM) and static random access memory (SRAM).
A GMR memory has a spin-valve structure that is composed of a pinned layer having a high coercive force and a free layer having a low coercive force. In the GMR memory, information writing is achieved by changing the spinning direction of the free layer using a produced magnetic field generated by a current applied to word lines and bit lines. Information reading is achieved by applying a current to the word lines and measuring a resistance from the bit lines.
A TMR memory has large magnetic resistance as compared to a GMR memory. Accordingly, if the TMR memory is used, a high signal may be obtained and power consumption may be reduced. However, when the TMR memory is downsized, an operating time thereof is lengthened and noise is increased, since the TMR memory has a significant amount of resistance, for example, about 106 Ω-μm2.
In such conventional MRAMs, when a cell size is reduced to a size of sub-microns or less, coercivity increases, and the thermal security of a cell degrades. These characteristics prevent a high level of integration.